Devices that have output luminance that are nearly that of its light source are often termed high-brightness devices. In many instances, it is difficult to achieve high-brightness devices for very small light sources, such as a single high-power LED (e.g., an LED with about 2 square millimeters of area), as compared to thousands of square millimeters for even a small display.
Providing high-brightness devices that employ small light sources can be beneficial in many instances. The cost and/or complexity of providing such devices can be prohibitive.